(1) Field of the Invention
The invention relates to a staple-forming apparatus for stapling machines and stapling heads. More particularly the invention provides a stapler housing having a displaceable pusher that serves as a stop during the staple forming operation as well as an ejecting element during stapling and has a locking bar moveably fitted in the pusher with a fixed stop on the housing for the locking bar.
(2) Description of Related Art Including Information Disclosed Under 37 C.F.R. 1.97 and 1.98
In order to staple material which is to be stapled, such as paper, cardboard or the like, use is made, according to the prior art (DE 44 44 220), in stapling machines of so-called stapling heads which, in addition to other components, have staple-forming apparatuses. In these stapling apparatuses, which are also referred to as forming means, a cut-to-length piece of wire is bent into a u-shaped staple before being driven, by means of a staple driver, into the paper stack which is to be stapled.
The staple driver in this case is usually fitted in a moveable manner on a pusher in a forming-means housing. In order to form the staple, the forming-means housing has two side guides, in each of which is provided a groove for guiding the wire. The two end legs of the staple are formed in said side guides. The pusher itself comprises a driver which is positioned thereon and has an accommodating groove in a direction transverse to the movement direction, so that the crosspiece of the staple is formed between the two end legs. The entire forming means is actuated via a drive acting on the pusher.
In order to form the staple, a locking means is provided in the pushing direction of the pusher, with the result that the pusher, as it strikes against said locking-means, carries along the entire forming-means housing and pushes it onto the cut-to-length wire located transversely therebeneath. During this movement of the forming means, the wire positions itself on the side guides of the forming-means housing, on the one hand, and, transversely thereto, on the driver of the pusher, with the result that the u-shaped staple forms.
Once the staple has been formed, it is ejected in that the locking means of the pusher is released and the latter is pushed in the pushing direction. The pusher pushes the staple in this operating cycle, for example, into a paper stack located beneath the forming means. If appropriate, it is also possible to provide guide aids in order to prevent warping of the side legs of the staple during the pushing-in operation.
Conventional forming apparatuses comprise a locking bar which is mounted in a displaceable manner in the forming-means housing and engages in a curved path provided on the pusher. Formed in this curved path is a stop which, together with the locking bar fastened on the frame, defines the forming position of the pusher in the forming-means housing.
The object of the invention is to propose a type of construction for a forming apparatus for stapling machines which makes possible a smaller design of the forming means.
This object is achieved, taking as the departure point a prior art of the type mentioned in the introduction, by the utilization of a locking bar moveably fitted in the pusher with a fixed stop on the housing for the locking bar.
Advantageous refinements and developments of the invention are possible by way of the measures mentioned in the subclaims.
Accordingly, a staple-forming apparatus according to the invention is distinguished in that a locking bar is fitted on the pusher such that it can be moved between a blocking position and a release position and a fixed mating stop for the locking bar is provided on the forming-means housing. Fitting the moveable locking bar on the pusher rather than, as in the case of the previously known prior art, on the forming-means housing then makes it possible to realize a locking means which has considerably reduced outer dimensions, since, up until now, it has been necessary for the guide of the transverse locking bar and the securing means thereof to be positioned to the housing of the forming means from the outside. According to the invention, now only a fixed mating stop, which does not take up any space, is required on the housing of the forming means since the actual locking bar is fitted on the pusher essentially in the interior of the forming means housing.
In a particularly advantageous embodiment of the invention, the locking bar is designed in the form of a pin which passes through the pusher in a direction transverse to the pushing direction. In addition to the locking bar being in a form which is particularly straightforward to produce and is easy to install, this ensures, at the same time, that the pusher is locked on both side guides in its blocking position, with the result that good force transmission can take place without tilting of the pusher.
In a development of this embodiment, a slot guide for the locking bar is provided in the housing of the forming means. This means that the locking bar is accessible from the outside in different positions of the pusher, which is advantageous, in particular, for installation and for actuation during the operation of the forming apparatus. The locking bar can be actuated, for example, by an actuating element acting directly on the locking bar.
It is also advantageous if the slot, in certain regions, has two different widths. This makes it possible, with the aid of a transverse displacement of the locking bar, for the blocking position to be locked and unlocked in a straightforward manner in that the locking bar has different diameters in certain regions. A larger diameter corresponds here to the larger width of the slot, while an axially offset, smaller diameter corresponds to the smaller width of the slot. Depending on the position of the locking bar, it is accordingly possible for the pin to pass through the narrow region of the slot or not. In the blocking position, the locking bar assumes a position by striking against the tapering of the slot by way of the larger diameter and thus being locked, while, in the release position, it can also be moved in the narrow region of the slot by way of the smaller diameter.
The slot advantageously has, at least in the region of its smaller width, a stepped formation in a direction transverse to the pushing direction of the pusher. This makes it possible for the displacement distance which is necessary for the unlocking and locking of the locking bar to be reduced. Furthermore, this design ensures that the locking bar essentially does not project beyond the outer contours of the forming means during operation and, in particular, during unlocking.
A restoring element, which pulls or pushes the locking bar into its locking position is preferably provided. This ensures automatic locking, with the result that actuation only has to take place for unlocking purposes. The restoring element may be designed, for example, in the form of a helical spring which is pushed onto the locking bar and butts against a stop on the locking bar, on the one hand, and a stop on the pusher, on the other hand. In this configuration, the locking bar is always pushed in its axial direction, i.e. in a direction transverse to the actuating direction of the pusher, in one direction by means of the helical spring.
A blocking member is preferably provided, it being possible for said blocking member to be fitted on the locking bar by means of a rotary closure. Such a blocking member makes it possible, for installation purposes, for the locking bar, with the helical spring positioned, to be pushed into the pusher from one side until it projects on the opposite side. It is then possible, on this opposite side, for a larger-diameter blocking member to be positioned and fastened by means of the rotary closure. This arrests the locking bar in the corresponding cutout of the pusher and/or of the forming means.
It is also advantageous if the blocking member has a rotation-prevention means. This ensures that the rotary closure of the blocking member on the locking bar is not released automatically during the operation of the apparatus.
In the same way, it is advantageous if, in addition, a rotation-prevention means is provided on the locking bar in order to prevent rotation of the pin relative to the blocking member, with the result that unintended release of the blocking member by rotation of the pin is likewise ruled out.